https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94050
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
So quite obviously *a* fix would be
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6705,6 +6705,7 @@ layout_class_type (tree t, tree *virtuals_p)
/* If we didn't end up needing an as-base type, don't use it. */
if (CLASSTYPE_AS_BASE (t) != t
+ && !CLASSTYPE_USER_ALIGN (t)
&& tree_int_cst_equal (TYPE_SIZE (t),
TYPE_SIZE (CLASSTYPE_AS_BASE (t))))
CLASSTYPE_AS_BASE (t) = t;
(needs a comment of course). Since the original fix was to avoid creating
extra copies for LTO purposes, this slight degradation should not be too bad?
